Zimmermann again pitched through the lingering neck soreness he has confronted for most of his all-star season. The ailment has vexed Zimmermann, and the Nationals have not been able to identify the precise source of the pain. Depending how he feels between now and Tuesday’s showcase, Zimmermann may have to skip his first all-star game.

“It’s a possibility,” Zimmermann said. “I’m not really sure yet what I’m going to do. We’ll see how the next few days go and then go from there.”

Zimmermann, sitting on a league-high 12 wins and a 2.58 ERA after he allowed two runs in 61/3 innings, will wait before he makes a decision about his participation. His neck felt better Thursday night than during his previous start, but the discomfort has not dissipated.

He has treated it with massage and heat, but the pain moves from one side of his neck to the other, sometimes on a day-to-day basis, Zimmermann said. If he is not convinced it has calmed down by the end of the weekend, he will prioritize the Nationals’ season over the Midsummer Classic.

The Post Sports Live crew debates whether Bryce Harper will have a more exciting appearance in the MLB All-Star Game or in the Home Run Derby. (Post Sports Live)

“I’d rather be healthy for the second half than pitch in that,” Zimmermann said. “I’d like to pitch in it, but I’m not going to go up there and pitch an inning and have to battle in the second half.”

The decision will arrive in the coming days. Thursday, left unsupported by a negligent offense, Zimmermann’s night hinged on his seventh-inning confrontation with Kevin Frandsen, who poked an 0-2 slider into right-center field, just out of Denard Span’s reach, for a go-ahead double.

Zimmermann earned his trip to Citi Field because he had so often pitched as well as, or better than, he pitched Thursday night. “Everyone talks about [Matt] Harvey starting the All-Star Game,” Frandsen said. “But that guy has made himself one hell of a resume all year.”

He could not be blamed for the Nationals’ third loss in four games at Citizens Bank Park. That fell to the Nationals’ offense, which managed five hits – three in the final eight innings – off right-hander Kyle Kendrick and two Phillies relievers.

Despite four Phillies errors, the Nationals scored two runs or less for the 40th time in 92 games. The Nationals will head into the final series before the all-star break at 47-45, back to six games behind the Atlanta Braves in the National League East.

“We just need to hit the reset button in general, whether we win three games out of three or get swept by them,” Span said. “We need to reset regardless.”

The Post Sports Live crew debates whether shortstop Ian Desmond is the Nationals’ MVP up to this point in the season. (Post Sports Live)

Thursday was another one of those nights when they abandon their starter. They did not generate many chances, but when they did, they quickly fizzled. They botched two sacrifice bunts, including one from Span, who mistakenly thought the ball had bounded foul and waited a beat to leave the batter’s box, leading to a double play.

“Every time we had an opportunity to score, we shot ourselves in the foot,” shortstop Ian Desmond said.

Zimmermann and Kendrick dueled to a 1-1 draw after 61/2 innings. Darin Ruf led off the bottom of the seventh with a double to left-center field. Carlos Ruiz bunted him to third base, and Phillies Manager Charlie Manuel sent Frandsen to pinch hit.

Zimmermann typically prefers weak contact to strikeouts, all the better to keep his pitch count low — Thursday, he struck out six and moved into the seventh with fewer than 75 pitches. Now, though, he needed a strikeout. A grounder could score pinch runner John McDonald, and a fly to the outfield almost certainly would.

Zimmermann jumped ahead of Frandsen with a slider and a fastball just off the outside corner, at which Frandsen could not check his swing. Frandsen fouled away the next pitch. Zimmermann went for the kill, another slider that started on the outside edge of the plate and broke away from Frandsen.

Zimmermann got the pitch out of the strike zone, but he left it at the belt. Frandsen poked it to right-center field. Span could not squeeze the ball, but either way McDonald would have trotted home with the go-ahead run.

“If I put it in the dirt, he’s swinging and missing,” Zimmermann said. “I left it up, and he was able to get one arm on it and reach out and get it.”

The Phillies had struck first. Ruiz reached in the fifth when his smash deflected off Zimmermann’s foot and trickled toward the right side of the infield. Kendrick moved him to second base with a sacrifice bunt. With two outs, pesky leadoff man Ben Revere lined a single to left-center field, his eighth hit of the series. Ruiz cruised home with the game’s first run.